Electroacupuncture regulates macrophage polarization via the TLR4/NF-κB signaling pathway to ameliorate endometrial injury in rats

Inflammatory response plays a critical role in the development of fibrosis in IUA. EA has shown promise in alleviating inflammation and fibrosis while promoting the repair of damaged endometrial tissue. This study aimed to explore whether EA promotes endometrial repair in a rat IUA model by modulating macrophage polarization. Specifically, we examined its effects on attenuating inflammation and fibrosis, with a focus on the underlying molecular mechanisms involving the TLR4/NF-κB signaling pathway. A rat model of intrauterine adhesion (IUA) induced by mechanical scraping combined with lipopolysaccharide (LPS) was used to evaluate the therapeutic effect of electroacupuncture (EA). Hematoxylin-eosin (H&E) staining was performed to observe endometrial morphology, the degree of intrauterine adhesion, and the number of glands and blood vessels in IUA rats. Fertility was assessed by mating experiments. Masson's trichrome staining was used to detect the extent of endometrial fibrosis. Additionally, RNA-seq was employed to analyze the effect of EA treatment on immune responses in the endometrial tissue of IUA rats. The expression of factors related to fibrosis and inflammation in endometrial tissue was detected by immunohistochemistry, Western blotting, and quantitative real-time polymerase chain reaction (qRT-PCR). Macrophage polarization was analyzed by immunofluorescence staining and flow cytometry. Statistical significance was set at P < 0.05. Compared with ctrl group, rats in the IUA group exhibited severe intrauterine adhesions, tissue fibrosis and abnormal endometrial function. Relative to the IUA group, EA-treated rats showed a more complete endometrial structure, morphology and function. At the molecular level, EA downregulated fibrosis-related factors and inhibited activation of the TLR4/NF-κB signaling pathway in endometrial tissue, resulting in decreased levels of the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. EA also promoted a shift in macrophage polarization from the pro-inflammatory M1 phenotype toward the reparative M2 phenotype. Notably, macrophage depletion with clodronate liposomes largely abolished the protective effects of EA on endometrial structural repair and functional recovery. Electroacupuncture attenuates IUA associated endometrial injury by suppressing excessive activation of the local TLR4/NF-κB signaling pathway, thereby reprogramming macrophage polarization, mitigating inflammation, inhibiting fibrosis, and promoting organized endometrial regeneration.